This invention relates to an improved firewall for protection of high-value and essential equipment such as high-voltage transformers in an electrical utility station. Transformers of this type typically contain a flammable oil which can ignite into a dangerous fire in the event of a major short circuit or other equipment failure or environmental problems. Such fires can reach very high temperatures which can spread the fire to adjacent equipment such as other transformers, putting in jeopardy the ability of the utility service to provide electrical energy.
The improved firewall is made of cementitious inorganic composite material which has good insulation and fire-resistant properties. In a presently preferred form the composite material is an inorganic phosphate cement as described in U.S. Pat. No. 6,103,007, the disclosure of which is incorporated herein by reference. The wall is preferably made in sections which are supported between spaced-apart vertically upstanding girders such as steel I beams. The beams are preferably protected by overlying sheets of glass-fiber fabric impregnated with the cementitious material.